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At work we've recently hired a few new developers and they got this error.
Having worked at setting up many development boxes in the past I knew what the issue was, but honestly I need to post about it so I have a quick reference to the fix... and I figured it may help you as well.
The problem? .NET framework was installed before IIS. The fix is pretty easy, you need to 'reinstall' the .NET framework. Thankfully Microsoft makes it fairly easy.
Open up a command line and type the following and you will be good to go.
c:\windows\microsoft.net\framework\v2.0.50727\aspnet_regiis.exe -i
Which will look something like this after the fact:
More info here.
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